Spring-force applying means

ABSTRACT

A spring-brake actuator wherein the piston acted upon by the spring is connected to its piston rod via a clutch held disengaged only so long as fluid pressure is effective on the piston to render the spring inoperative to apply the brake.

United States Patent Higgins [54] SPRING-FORCE APPLYING MEANS [72]inventor: Horatio Leslie Higgins, London, En-

gland [73] Assignee: Westinghouse Brake and Signal Company Limited,London, England 22 1 11611; March 11, 1971 121 Appl.No.: 123,271 v [30]Foreign Application Priority Data May 21, 1970 Great Britain ..24,630/70[52] U.S. Cl ..92/29, 188/170 [51] lnt.Cl ..F0lb 9/00 [58] Field ofSearch 92/91, 91 A, 70.27, 94, 85 CA; 92 3, 29, 24; 1ss/170 [56]References Cited UNITED STATES PATENTS 2,722,301 11/1955 Francois ..192/94X Dec. 5, 1972 3,145,816 8/1964 DeLorgan et a1. ..l92/91 A 3,464,5289/1969 Mork et a1. 192/91 R 3,540,557 ll/1970 l-lasselbacher ..192/91 AFOREIGN PATENTS OR APPLICATIONS 765,330 12/1933 France ..l92/9l A 46,4437/1939 Netherlands ..192/85 Primary Examiner-Martin P. SchwadronAssistant ExaminerR. H. Lazarus Attorney-Larson, Taylor & Hinds [5 7]ABSTRACT .A spring-brake actuator wherein the piston acted upon by thespring is connected toits piston rod via a clutch held disengaged onlyso long as fluid pressure is effective on the piston to render thespring inoperative to apply the brake.

5 Claims, 3 Drawing Figures SPRING-FORCE APPLYING MEANS This inventionrelates to spring-force applying means having a spring which exerts itsforce across a pair of members relative displacement of which in onedirection under the influence of the spring causes the spring to apply aforce on a force transmitting element, and a chamber defined at least inpart by the pair of members to which chamber can be applied a fluidpressure which exerts across the members a force opposing that exertedby the spring whereby the members are relatively displaced in theopposite direction at least partially to relieve the element of theforce otherwise applied thereto by the spring. Such spring-forceapplying means will hereinafter be referred to as of the type described.

Spring-force applying means of the type described can be used as brakeactuators for applying the brakes of either a road or a rail vehicle. Inthis case, the element is connected to a brake of the vehicle. Suchbrake actuators may be the sole form of brake-applying means or may beadditional to the conventional fluidpressure or electrically operatedbrake applying means as an emergency and/or brake applying means.

The present invention provides a spring-force applying means of the typedescribed, wherein the forcetransmitting element is operativelyconnected to one of the pair of members through a clutch engaged whenthe pressure in the chamber is below a pre-determined value thereby topermit (upon the relevant displacement of the members by the spring insaid one direction) the spring to apply a force on the element, theclutch being disengaged upon the application of the fluid pressure tothe chamber when that fluid pressure exceeds said predetermined value sothat the element can move freely in either direction relative to saidone of the members.

The clutch may be constituted by a nut threadedly engaged through areversible thread with the element, the nut having a clutch facecooperable with a complementary clutch face on said one of the members.The nut may be urged by a second spring in a direction to engage theclutch faces, the value of the spring determining the predeterminedvalue of pressure in the chamber at which the clutch is engaged ordisengaged respectively. The nut, in operation of the means, may bemoved against the force exerted by a second spring thereby to disengagethe clutch by the fluid pressure in the chamber being applied to apressure responsive member operative on the nut. There may be interposedbetween the nut and the second spring a first thrust bearing and betweenthe nut and the pressure-responsive member a second thrust bearing; thebearings may each be a ball-bearing.

An embodiment of the present invention which is also described incommonly owned copendin U.S. application Ser. No. l23,272, filedconcurrently with this application, will now be described in greaterdetail, by way of example only, with reference to the accompanyingdrawings of which:

FIG. 1 is a cross-sectional view of the spring force applying means,

FIGS. 2 and 3 diagrammatically illustrate brake-applying means for arail vehicle incorporating the springforce applying means of FIG. 1.

Referring, firstly, to FIG. 1; the spring-force applying means (which,in this case, is a spring-brake actuator) comprises a pair of members 1and 2 of which the member 1 is a fixed cylinder and the member 2 is apiston slidable within the cylinder. The piston 2 divides the cylinder 1into two chambers 3 and 4.

Within the chamber 3 is a pair of heavy compression springs 5 one end ofeach of which abuts the piston 2 and the other end of each of whichabuts the end wall 6 of the cylinder 1 so that the springs 5 exertacross the members 1 and 2 a force tending to move the piston 2 to theleft as viewed in the drawing. Opening into the chamber 4 is a port (notshown) by which fluid under pressure can be applied to the chamber 4.

The limits of the stroke of the piston 2 are determined (in thedirection to theright as viewed in the drawing) by a stop-face 7 carriedby the piston 2 engaging the end wall 8 of the cylinder 1 and (to theleft as viewed in the drawing) by a stop-face 9 on the interior of theend wall 8 of the piston l engageable by the face 10 of the piston 2.

The piston 2 provides a first clutch face 11 engageable by acomplementary cooperable clutch face 12 on a nut 13. The nut 13 isthreadedly engaged through a reversible thread at 14 with aforce-transmitting element 15. The element 15 is guided at itsright-hand end (as viewed in the drawing) by a bush 16 located on theelement 15 between a shoulder 17 and a circlip 18 (the bush 16 beingslidable within a bore 19 in a pressureresponsive member 20) and, at itsleft-hand end (as viewed in the drawing) by the circumferential wall 20of a rod-like extension 22 of the element 15 (the circumferential wall21 being slidable within a bore 23 of a part 24 fixed to the piston).The rod-like extension 22 has extending across it a cut 25 from whichprojects a thrust member 26 pivotally mounted on the extension 22 by apivot-pin 27. The outer end of the thrust member 26 is pivotallyconnected by a pivot-pin 27 with an arm 28.

Returning to the nut 13, there is located one on each side of the nutthrust bearings 29 and 30. The thrust bearing 29 is located between thenut 13 and an abutment 31 between which and an end face 32 of the part24 is a compression spring 33. The thrust bearing is located between thenut 13 and the end face 34 of the pressure-responsive member 20. Thepressure-responsive member 20 is in the form of a piston slidable withinbores 35 and 36 in the piston 2. Between the piston 20 and the piston 22is a chamber 37 connected to the chamber 4 via a conduit 38.

Threadedly engaged at 39 with the piston 2 is a rotatable member 40which has an end face 41 engageable with a face 42 on the piston 20. Atthe opposite end of the rotatable member 40 from the face 41 are dogs 43interdigitated with dogs 44 on a further rotatable member 45 locatedwithin the piston 2. Extending between the piston 2 and the furtherrotatable member 45 is a torque spring 46 the tails 47 and 48 of whichare engaged respectively in a hole 49 in the piston 2 and a hole 50 inthe member 45. Projecting from the member 45 outwardly of the cylinder 1is a box 51.

The above-described actuator operates as follows:

Assuming that the pressure in chamber 4 is at atmospheric pressure, thesprings 5 will move the piston 2 to the left (as viewed in the drawing)and, because there will likewise be atmospheric pressure in the chamber37, the spring 33 will, through the thrust bearing 29, spin the nut 13along the element 15 to inter-engage the clutch faces 11 and 12. Thus,leftward movement of the piston 2 under the influence of the springs 5will cause the force exerted by the springs 5to be transmitted to theelement 15 via the piston 2 and the nut 13. The element 15 willtherefore also be moved to the left carrying with it the thrust member26 to apply the force exerted by the springs 5 on the arm 28.

' In order to relieve the arm 28 of the force exerted by the springs 5through the force-transmitting element 15, fluid pressure is introducedinto the chamber 4 through the port (not shown) and this pressure, whenit has built-up to a sufficient value, will, overcome the force exertedby the spring Sto returnto. the right the piston, to its position asshown in the drawing. Meanwhile, the pressure applied to the chamber 4will be transmitted to the chamber 37 throughthe conduit 38 to move thepiston 20 to the left against the effort exerted by the spring 33so-that when the pressure in the chamber 37 exceeds a predeterminedvalue (determined by the value of the spring 33) the clutch faces 11 and12 will be disengaged so as tofree the arm 28 of the force exertedthereon by the springs 5.

As, conventionally, the arm 28 will have operative on it a return-spring(not shown), the arm 28 and the force transmitting element 15 willreturn to the right with the piston 2.

With the force on the arm 28 relieved, as above described, by thepressurization of the chamber 4, the chamber 37 will also be pressurizedas above described. With the pressurization of the chamber 37, thespring 33 is overcome so that the clutch faces 11 and 12 are disengagedand the nut 13 is supported between the thrust bearings 29 and 30. Inthis condition, the arm 28 can freely be moved as the force-transmittingelement 15 can move axially with the nut 13 spinning idly on thebearings 29 and 30.

If it is necessary manually to release the brakes operated by theactuator at any time (for example, for the purpose of renewing the brakeblocks), this. is achieved in the following manner:

Firstly, the chamber 4 (and therefore, the chambers 37) arede-pressurized so that the brakes will'be applied in the mannerabove-describedby the springs 5. By the use of a spanner applied to thehex 51, the member 45 can be rotated against the effort of the torquespring 46 so as similarly to rotate the member 40 through theinterdigitated dogs 43 and 44. By virtue of the threaded connection at39 of the member 40 with the piston 2, such rotation of the member 40will cause member 40 to move to the left so that the face 41 of themember 40 engages the face 42 of the piston 20. Further rotation of themember 45 (and therefore, the member 40) will move the piston to theleft against the effort of the spring 33 and thus disengage the clutchfaces 11 and 12. Such disengagement of the clutchfaces 11 and 12 willfree the piston 2 from being clutched to the force-transmitting element15 and this produces two results. Firstly, the piston 2 will continueits movement to the left under the influence of the springs 5 until theface 10 of the piston 2 abuts the stop face 9 on the interior of the endface 8 of the cylinder 1 and, secondly, the conventional return springoperative on the arm 28 will move that arm and the force-transmittingelement 15 to the right (as viewed in the drawing) while the nut 13spins freely on the-thrust bearings 29 and 30 as the clutch faces 11 and12 are now disengaged. Thus, although the piston 2 is what wouldnormally be its brake-applying position, the brakes will, in fact, bereleased by the return-spring (not shown) normally operative on the arm28.

As soon as the member 45 is allowed to return (under the influence ofthe torque spring 46) to its original position upon the removal of thespanner from the hex 51, the member 40 will be rotated with the member45 by the torque spring 46 back to its original position in which thefaces 41 and 42 are disengaged thus allowing the spring 33 to re-engagethe clutch faces 11 and 12. After replacement of the brake blocks, thesystem is restored to its normal mode of operation by re-pressurizationof the chambers 4 and 37.

The above-described actuator can be applied in conventional rail-vehiclebraking systems as illustrated in FIGS. 2 and-3. I I In the system ofFIG. 2, the actuator above described is diagrammatically represented bythe box 60 from which projects the thrust member 26 pivotally connectedat 27 tothe arm 28. Pivotally connected to the upper end (as viewed inthe drawing) of the arm 28 is the piston rod 6l of a conventionalairapplied brake actuator 62. The arm 28 is pivotally connected at 63 toa fixed mounting 64 and the lower end (as viewed in the drawing) of thearm 28 is pivotally connected at 65 to the conventional brake shoe 66.

In a normal service application, the brakes would be applied by theconventional air-applied brake actuator 62 application of air pressureto which would extend the piston rod 61 from the actuator 62 to pivotthe arm 28 about the pivot 63 is an anti-clockwise direction to applythe brake shoe 66 to the wheel 67. Considering the brake actuator 60, insuch a normal service application the chamber 4 and chamber 37 would bepressurizedso that, firstly, the springs 5 were held compressed with thepiston 2 in its position as shown in FIG. 1 and the spring 33 compressedby the application of the fluid pressure to the chamber 37 moving thepiston 20 to the left (as viewed in FIG. 1) thus disengaging the clutchfaces 1 1 and 12. Hence, as the arm 28 pivots in its anti-clockwisedirection the thrust-transmitting element 15 will be free to move to theleft (as viewed in FIG. 1) idly spinning the nut 13. Conversely, as thebrakes are released by de'pressurization of the actuator 62 and theconventional return spring (not shown) returns the arm 28 in a clockwisedirection about the pivot 63, the force-transmitting element 15 can bedrawn to the left through the nut 13 which again will idly spin as theclutch faces 11 and 12 continue to be held disengaged by the applicationof fluid pressure to the chamber 37.

Should there be a failure or loss of pressure of or in the actuator 62,the brakes can be applied by reducing or removing entirely the pressurefrom chamber 4. If the pressure in chamber 4 is only partially removedthis can be removed in a controlled manner so as gradually to apply thebrakes. This will occur by virtue of the fact that with increasingreduction of the pressure in the chamber 4, the springs 5 will exert anincreasing effective pressure on the piston 2 moving it to the left thusre-engaging the clutch faces 11 and 12 and applying the braking forcethrough the piston 2, the nut 13, the

force-transmitting element 15, the thrust member 26, and the arm 28 if,of course, the chamber'4 (and therefore, the chamber 37) is completelyde-pressurized, the springs 5 will exert their full effect to exertmaximum braking effort.

Additionally, the actuator 60 can be used as a parking brake for whenthe rail vehicle is parked, all systems will be de-pressurized so thatagain, the springs 5 will be full effective to exert the braking effort.

FIG. 3 shows an alternative arrangement to that of FIG. 2. In FIG. 3 twofurther alternatives are shown. That shown in full lines shows anarrangement with the conventional brake actuator 62 back-to-back withthe actuator of FIG. 1. In this case, the thrust member 26 of theactuator 60 is connected to the arm 28 as previously described but thepiston rod 61 of the conventional actuator 62 is connected to a secondarm; the two arms 28 and 68 being interconnected with a tie bar 69 andeach being pivotally connected at its lower end (as shown in thedrawing) at 70 at the brake rigging 71 of conventional configuration.

Instead of the back-to-back arrangement shown in full lines, theactuator 60 may be (as shown in dotted lines) arranged in parallel withthe conventional actuator 62. Again as is conventional, while the pistonrod 61 of the conventional brake actuator 62 would be con nected to thearm 68, the cylinder of the actuator 62 would be connected to the upperend (as shown in the drawing) of the arm 28. As regards the actuator 60,the thrust member 26 would again be pivotally connected to the arm 28but the cylinder 1 of the actuator 60 would be connected by a bar 72 tothe arm 68.

The operation of the system shown in FIG. 3 will be clear to thoseskilled in the art from the description which has been given above withrespect to the arrangement shown in FIG. 2.

By virtue of the pressure in chamber 37 being released through conduit38 and chamber 4, there may be delay in release of pressure from chamber37 relative to release of pressure from chamber 4. Should this be so,then there might result some extension (albeit minimal) of spring 5prior to inter-engagement of clutch faces 11 and 12. If such beobjectionable, then the supply and withdrawal of pressure to and fromshoulders 4 and 37 could be effected from a point in conduit 38 with achoke being positioned in the conduit 38 between that point and thechamber 4 thus to delay the release of pressure in chamber 4 relative torelease of pressure in chamber 37.

Having thus described my invention what I claim is:

l. A spring force applying means comprising a pair of members relativedisplacement of which in one direction under the influence of a springcauses the spring to apply a force on a force transmitting element and achamber defined at least in part by the said pair of members to whichchamber can be applied a fluid pressure which exerts across the membersa force opposing that exerted by the spring to displace the membersrelatively in the opposite direction to at least partially relieve saidforce transmitting element of the force otherwise applied thereto by thespring, and wherein the force transmitting element is operativelyconnected to one ,of the pair of members through a clutch which engageswhen the pressure in the chamber is below a predetermined value to causethe spring thereof to apply a force on the element upon the relevantdisplacement of the members by the spring in said one direction, theclutch being disengaged upon the application of fluid pressure to thechamber when that fluid pressure exceeds said predetermined value, theengagement of said clutch and said force transmitting element includingfor allowing the said force transmitting element to move freely relativeto said clutch when the clutch is disengaged.

2. A spring-force applying means as claimed in claim 1, wherein theclutch is constituted by a nut threadedly engaged through a reversiblethread with the element, the nut having a clutch face cooperable with acomplementary clutch face on said one of the members.

3. Spring-force applying means as claimed in claim 2, wherein the nut isurged by a second spring in a direction to engage the clutch faces, thevalue of the spring determining the pre-determined value of pressure inthe chamber at which the clutch is engaged or disengaged respectively.

4. Spring-force applying means as claimed in claim 3, wherein the nut,in operation of the means, is moved against the force exerted by asecond spring thereby to disengage the clutch by the fluid pressure inthe chamber being applied to a pressure responsive member operative onthe nut.

5. Spring-force applying means as claimed in claim 4, wherein there isinterposed between the nut and second spring a first thrust bearing andbetween the nut and the pressure responsive member a second thrustbearing.

1. A spring force applying means comprising a pair of members relativedisplacement of which in one direction under the influence of a springcauses the spring to apply a force on a force transmitting element and achamber defined at least in part by the said pair of members to whichchamber can be applied a fluid pressure which exerts across the membersa force opposing that exerted by the spring to displace the membersrelatively in the opposite direction to at least partially relieve saidforce transmitting element of the force otherwise applied thereto by thespring, and wherein the force transmitting element is operativelyconnected to one of the pair of members through a clutch which engageswhen the pressure in the chamber is below a predetermined value to causethe spring thereof to apply a force on the element upon the relevantdisplacement of the members by the spring in said one direction, theclutch being disengaged upon the application of fluid pressure to thechamber when that fluid pressure exceeds said predetermined value, theengagement of said clutch and said force transmitting element includingfor allowing the said force transmitting element to move freely relativeto said clutch when the clutch is disengaged.
 2. A spring-force applyingmeans as claimed in claim 1, wherein the clutch is constituted by a nutthreadedly engaged through a reversible thread with the element, the nuthaving a clutch face cooperable with a complementary clutch face on saidone of the members.
 3. Spring-force applying means as claimed in claim2, wherein the nut is urged by a second spring in a direction to engagethe clutch faces, the value of the spring determining the pre-determinedvalue of pressure in the chamber at which the clutch is engaged ordisengaged respectively.
 4. Spring-force applying means as claimed inclaim 3, wherein the nut, in operation of the means, is moved againstthe force exerted by a second spring thereby to disengage the clutch bythe fluid pressure in the chamber being applied to a pressure responsivemember operative on the nut.
 5. Spring-force applying means as claimedin claim 4, wherein there is interposed between the nut and secondspring a first thrust bearing and between the nut and the pressureresponsive member a second thrust bearing.